Generally when the physiologically active agents are absorbed into a physical body through skins or mucous membranes, medicinal substances administered through skins or mucous membranes have been studied positively due to the fact that the medicinal substances of this type have some advantages that they show a convenience in administering, keeping a blood concentration and a capability of avoidance of side effects of physiologically active agents against a digestive canal or the like as compared with an oral administering. In particular, as a local administering method which is effective for promoting absorption of physiologically active agents through skins or mucous membranes, iontophoresis has been noticed.
Iontophoresis is a kind of method for promoting physical absorption of physiologically active agents, wherein a certain voltage is applied to either skins or mucous membranes to cause the physiologically active agents to generate electrophoresis and further physiologically active agents to be administered through skins or mucous membranes.
A usual type of plaster structure for iontophoresis has a configuration in which a medicinal substance storing layer for use in storing physiologically active agents and the electrodes are combined to each other and various kinds of additive agents as required in addition to physiologically active agents of a pre-designed specified amount are enclosed in the medicinal substance storing layer in order to administer a controlled amount of physiologically active agents continuously to a physical circulating system for a specified period of time so as to keep a stable medical effect.
As the plaster structure for iontophoresis satisfying these requirements, various kinds of structures have been disclosed in the gazettes of Japanese Patent Laid-Open No. Sho 62-268569 or 63-102768, Japanese Utility Model Laid-Open No. Sho 64-50844, Japanese Utility Model Laid-Open No. Hei 2-53757 and Japanese Patent Laid-Open No. Hei 3-45271 or the like.
However, it has been found that these prior art configurations described above have some problems that either the physiologically active agents or additive agents or the like are leaked out of the medicinal substance storing layer or dispersed and immersed into the adhesive agent layer by a time in which the plaster structure for iontophoresis is applied to a patient, resulting in that the actual amount of substances is reduced by less than the predetermined amount of physiologically active agents and medical effectiveness or durability or reliability is reduced. In addition, the physiologically active agents or additive agents or the like are immersed into the adhesive agent layer, resulting in that a problem occurred that an adhering force of the adhesive agent to skins or mucous membranes was weakened and the agent might easily be peeled off. As per the item in which a pressure-sensitive adhesive agent layer was provided at a releasing surface for the physiologically active agents, it had a problem that a serious influence was applied to a continuous and uniform application of the physiologically active agents under a mutual action between the physiologically active agents or additive agent and the adhesive agent layer when the item was applied to a patient or the adhesive agent layer was deteriorated or its durability was deteriorated.
This invention resolves the aforesaid problems of the prior art and it is an object of this invention to provide a plaster structure for iontophoresis in which a predetermined amount of physiologically active agents initially set can be stably kept or held without any loss until it is applied to a patient and when the item is applied to the patient, the predetermined amount of physiologically active agents initially set can be applied continuously to an entire body of the patient and concurrently a mutual action between the physiologically active agents or additive agents and the adhesive agent is prevented, an adhering power of the adhesive agent is kept and it may not be peeled off during its application.